PyTest Fixtures & Fleshing Out Your Stack Class

In VS code if you want to fix the import error you can add your virtual environment to workspace settings.

Open the settings.json file in .vscode directory

Then add the following:

{
    "python.venvPath": "~/patht/to/venvDirectory"
}

Correction, use this:

{
    "python.pythonPath": "/path/to/your/venv/bin/python",
}

Question! Are these ‘unit tests’ or ‘integration tests’? I couldn’t figure out the difference from the written tutorial. These seem like unit tests to me, but I don’t really know what the difference is functionally.

The main goal of unit testing is to verify a single component’s correctness in isolation from the outer world. Integration tests, on the other hand, let you check if those individual components can work together.

Both kinds of tests serve a different purpose, so you should exercise both.

For example, you may assert that each cabinet’s drawer can be successfully opened and closed, but when you put two of them at a corner, you won’t be able to open both at once, because the open one would block the other.

Testing a stack that doesn’t interact with other components is a unit test, I’d say. A “component” or “unit” typically translates to a Python class.

In the middle of this video, when we are passing from: write the test for push, and then, write the push method: My pytest.fixture is this:

@pytest.fixture
def stack():
    return stack.Stack()

I got this different error:

AttributeError: ‘function’ object has no attribute ‘Stack’

but If I rename the fixture into another name, like stack_def

@pytest.fixture
def stack_def():
    return stack.Stack()

and then I use also this new name inside test_push:

def test_push(stack_def):
    stack_def.push(3)
    assert len(stack_def) == 1

I solve the previous error, and I get the normal one, about the attribute ‘push’found:

AttributeError: ‘Stack’ object has no attribute ‘push’

So, it seams we are overriding the name stack, someway ? and we can’t use a fixture with the same name of the class?

I have Python 3.6 and a virtual environment.

@RobyB That’s right. More specifically, it’s a name collision because you try to use the same name for two different purposes:

1. Your fixture function
2. A module, which defines the Stack type

You have several options to mitigate that. For example, you could rename the module at the import time:

import stack as pile

@pytest.fixture
def stack():
    return pile.Stack()

Alternatively, you could import Stack without importing the enclosing module:

from stack import Stack

@pytest.fixture
def stack():
    return Stack()

A common naming convention in Python that lets you avoid collisions like that is to append a trailing underscore (_) to one of the names, e.g.

import stack

@pytest.fixture
def stack_():
    return stack.Stack()

This isn’t TDD though is it, the point of TDD is to shape code through tests which are driven by problem analysis.

TDD life-cycle

1. Get requirements.
2. Design components.
3. Write tests for all components.
4. Make sure all tests fail.
5. Write bare minimum of code to pass tests.
6. Refactor, test, repeat.

Am I wrong?